Posts Tagged ‘lake’

This update introduces supplementary hydrography features in North America and Europe that quadruple (4x) the number of lakes and rivers there. Many thanks to Tom P. for generalizing the vectors and Preston M. for adding tapering to North America (absent in Europe). In some cases the basic 10m rivers and lakes were modified to fit the new information and that’s been refreshed, as well. The North America data comes from the CEC North America Environmental Atlas. The Europe data extract is kindly provided into the public domain by the European Commission, Joint Research Centre (JRC), thanks Alfred J! Check out their original, higher resolution Europe data.

On the cultural front, North America gets roads and rails. General 10m detail roads and railroads come from the CEC North America Environmental Atlas. The supplementary roads are donated by XNR Productionsand are at 1m scale, thanks Laura M. and Rob!

If you have data or time to contribute, especially to flesh out the new transportation and hydro themes, please contact me at nathaniel@naturalearthdata.com.

Note: We are not committing to building out supplementary level of detail in the rest of the world (we’re not THAT crazy!), but will incorporate such data if you contribute it. As always, we edit these data files but you should too before you publish maps using them. Feed us back corrections.

(below) Rivers and lakes in North America. On the left the version 1.1 hydro features. On the right in color are the new, supplemental version 1.2 hydro features, 4x the density of features at the same 10m linework generalization.

(below) Rivers and lakes in Europe. On the left the version 1.1 hydro features. On the right in color are the new, supplemental version 1.2 hydro features, 4x the density of features at the same 10m linework generalization.

Tom and I have been busy adding 4 times the rivers and 3 times the lakes we had for North America. This adds in many “missing” hydro features that one might normally find on a 1:10,000,000 hydrologic reference map.

Why were they missing from the first version of Natural Earth? It’s hard to wade thru 1:1,000,000 features to figure which to add and an even tougher job to attribute them with the correct name and scale ranks. There’s another factor: these extra features are great if you’re making a watershed map, but can be a little noisy when used as a background layer in say a political reference map.

Cody Rice, now of the EPA but formerly of the Commission for Environmental Cooperation (CEC) send along an amazing link last week. The CEC is a joint agency between the United States, Canada, and Mexico. Specifically: USGS, Natural Resources Canada, INEGI-Mexico. Each country contributed base data for a 1:10,000,000 digital atlas. The data is available in many popular formats and is in the public domain. Better yet, it includes GIS data attributes like river name!

We’ve compared with our existing Natural Earth linework and identified which features were missing. For those we’re adding, we’ve adjusted the new linework a nudge here and there so it lines up with SRTM relief and our existing linework. We’ve also gone thru and created lake centerlines and applied scale ranks to all in three new steps (10, 11, and 12). We have some final polishing but will be releasing, along with some slight adjustments to the original data, by the end of January.

Do you have time to donate? Unlike ranks 0 to 9 (the original data), this new data will NOT come tapered. We’d like it to be and can show you how.

Know of a similar, attributed with name, 1:10,000,000 regional dataset we could adapt into Natural Earth to build out our coverage? Please let me know at nathaniel@kelsocartography.com.

Preview images below:

Red = new at rank 10. Blue = new at rank 11. Black = new at rank 12. Grey = old at ranks 0 to 9.

[Editor’s note: This Q&A from Environment Canada explains the rough difference between types of hydrological features. Names in the real world are often messier than this text book explanation. One way we’ve tried to help in Natural Earth is by indicating if a lake is freshwater, saline, natural, artificial, stable water level, seasonal water level, or simply ephemeral.]

What is the difference between a sea and a lake? Looking at the names of many sea and many lakes does not readily demonstrate an identifiable difference. There are salt water lakes and fresh water seas and some lakes that are bigger than other seas.
Bruce Schoenegge, Irvine, California, USA

Salt crust resulting from receding lake, Lake Frome, Australia.

In order to understand why some smaller salt water bodies are called lakes and others seas it is necessary to realize that lakes are, in geological time scales, transitory in nature–they form, mature and die.

Some water bodies that started out as saltwater seas over time became closed-off from the oceans. Depending on the quantity of fresh water flowing in from rivers, glacial melt water, or other sources, the salinity could have declined to the point where the water became relatively fresh. The Sea of Aral is probably an example of where this transition has occurred. Similarly the reverse can occur whereby freshwater lakes can become open to the sea so that the salinity increases, as in the Baltic Sea. The Black Sea is an example that has alternated between fresh and salt water conditions over geological time. Evidence for these changes can be found in ancient fossils of organisms some of which were known to be tolerant of saltwater while others were known to have been intolerant.

No doubt there was also some confusion in the naming of water bodies by the early explorers based on their first impressions and certainly one can understand why some may have been inappropriately named. In addition the subsequent translation of the names between different languages could also have added to the confusion.

Here are some definitions of water bodies:

Ocean

The whole body of salt water that covers nearly 3/4 of the surface area of the globe. In particular, each of the main areas into which the sea is divided geographically, e.g. Atlantic, Pacific. Oceans are tidal, living systems containing a multitude of biological organisms.

Average depth of the world’s oceans: 3,962 metres(13,000ft)

Maximum depth: 10,680 meters; (35,040ft)

Average salt content – 3.5% (mostly common salt, NaCl but with some magnesium and calcium salts)

Average density – 1.026

Sea

The expanse of salt water that covers most of the earth’s surface and surrounds the land masses. A body of salt water that is secondary in size to oceans.

Lake

A large area of water surrounded by land. Normally fresh water but in some cases can be appreciably saline depending on the geology of the underlying and surrounding terrain. Lakes are living systems containing various quantities of biological organisms. Lakes can be classified according to the level of bioproductivity as oligotrophic (low productivity), mesotrophic or eutrophic (high productivity). The productivity is usually controlled by the amount of nutrients (mostly phosphorus and nitrogen) present in the water and the amount of light that can penetrate the water column.

River

A large natural stream of water flowing in a channel to the sea, a lake or another such river. The flow can be permanent of seasonal.

Stream

A small, narrow river flowing on the surface of, or beneath, the ground.